@article{oai:repo.qst.go.jp:00078448,
 author = {Nomura, Takuji and Yamamoto, Yuji and Yoshii, Kenji and Takuji, Nomura},
 issue = {2},
 journal = {Journal of the Physical Society of Japan},
 month = {Jan},
 note = {We report a mean-field theoretical study of a triangular lattice magnet NiGa2S4. Specifically, spiral mean-field theory is applied to a 17-band d–p model constructed from the maximally localized Wannier functions. Our itinerant-model approach shows that the most stable spiral magnetic state has an ordering vector near Q=(0.15,0.15,0), consistent with neutron scattering experiments, when we assume the Ni-site Coulomb interaction is not so strong (U ≈ 2 eV). To map onto a classical Heisenberg spin model, we estimate spin exchange interactions from the mean-field results, and find that the nearest-neighbor exchange is ferromagnetic and the largest (larger than the third nearest-neighbor exchange, in contrast to early studies). We also calculate the dynamical spin correlation function S(q,ω), using the same model within the random-phase approximation (RPA). Calculated S(q,ω) has a spectral structure quite different from that of conventional spin-wave excitations.},
 title = {Weak-coupling Mean-field Theory of Magnetic Properties of NiGa2S4},
 volume = {89},
 year = {2020}
}